1. Field of the Invention
The present invention is directed to elastic strap material and specifically to a fire resistant, self-extinguishing strap material especially adapted to be used in conjunction with equipment likely to be exposed to flame environments, such as firemen's helmets, breathing masks, aircraft accessory pockets, etc.
2. The Prior Art
Many types of equipment which must necessarily be exposed to high temperature conditions and direct flame environments, such as firemen's masks, mine safety equipment and the like, desirably are provided with elastic retaining straps to facilitate donning and removing the equipment. Similarly, in commercial aircraft it is desirable to provide elastic strap components for use in connection with a variety of accessories while at the same time it is important that combustible items be minimized.
Elastic strap materials heretofore known have inevitably been supportive of combustion since such materials necessarily employ elastomeric compositions which burn readily.
Conventional attempts to make fire resistant elastic strap materials have involved combining in a woven or knitted fabric, elastomeric yarns and yarns of fire resistant material, such as Nomex (a registered trademark of DuPont Corporation) which is an aramid fiber which maintains its load carrying capacity at relatively high temperatures, does not burn or melt, but degrades at about 700.degree. F. (371.degree. C.)
Prior art strap material of the type described has proven ineffective in that the elastomeric components readily burn despite their combination with fireproof yarns.
We have discovered that the deficiencies of prior art elastic strap materials are engendered by the fact that in all such structures some portion or portions of the elastomeric and hence combustible components are exposed to oxygen in the atmosphere. Such exposure results from a fabric structure wherein loops of the elastomer providing elasticity are present at the surface of the fabric and by the necessity, in elastic fabric structures heretofore known, to weave or knit the non-elastomeric fibers loosely so that such fiber yarns do not inhibit or prevent stretching of the elastomeric components. The presence of elastomers at the surface of the strap results in combustion, liquefaction and wicking of the molten elastomer, and the loosely knit fabric promotes combustion by allowing oxygen to penetrate throughout the fabric weave.
No elastomeric containing fabric heretofore known has been capable of exhibiting a significant resistance to combustion.